Excess flow valves are commonly used in the gas industry. These valves are commonly used in gas gathering and gas delivery systems and are intended to regulate the flow of gas, vapour, liquid or multi-phase fluid therethrough by limiting the flow rate to a predetermined maximum rate. They are also used in other fluid distribution systems such as water distribution systems. A typical excess flow valve comprises a sliding poppet inside a chamber capable of closing an opening in the chamber, and preventing the flow of fluid or gas therethrough. A spring is often used to urge the poppet to its open position away from the opening. As the flow rate reaches or exceeds the maximum rate, such as the rate allowed by the size of the opening and/or the force of the spring, the pressure differential causes the poppet to slide toward the opening, against the force of the spring, to regulate or close the valve. A difficulty, however, of using standard excess flow valves is that they cannot be adjusted and therefore cannot be used where the fluid or gas supply pressures and threshold flow rates may vary, without changing the valve or components of the valve.
Certain types of externally adjustable valve systems have been used in the past to enable systems to be adjusted to different flow rates and pressures without having to substantially replace critical components each time an adjustment is made. Such adjustment capabilities are designed to alleviate the difficulty of having to replace internal components, such as the spring, or change the size of the opening, each time different flow rates and pressures are encountered.
U.S. Pat. No. 6,019,115, issued on Feb. 1, 2000 by R. Gene Sanders describes an excess flow valve having a threaded member extending through the valve, which causes a retainer, threadably located on the member to move laterally within the camber. The threaded member that extends from outside the housing into the center of the bore requires additional seals to seal the bore.